The polypyrrole (PPY)-modified electrode made through electropolymerization of pyrrole monomer is found sensitive to different cations depending on the dopants present within microstructure of polymeric domain. When p-toluenesulfonate (PTS) anion is doped, the modified electrode is sensitive to proton whereas, under similar conditions, in the presence of tetraphenylborate (TPB) anion, the same is sensitive to zinc ion. A comparative study on ion sensing behavior of PPY-modified electrodes is reported in this communication. The electro-polymerization of PTS-doped PPY-modified electrode, made under both potentiodynamic and potentiostatic conditions, are studied. The modified electrode is characterized by scanning electron microscopy and cyclic voltammetry and compared with those recorded for TPB-doped PPY-modified electrode made under similar conditions. The results based on scanning electron microscopy and cyclic voltammetry suggested; (i) dependence of microstructure based on mode of electropolymerization; (ii) dopantdependant ion sensitivity of PPY-modified electrode, (iii) variation in the redox behavior of the PPY-modified electrode based on dopants and mode of electropolymerization. Typical results on pH sensing together stability of PPY-based pH sensor are reported and compared with those recorded for polyaniline (PANI)-based pH sensor. (c) 2007 Wiley Periodicals, Inc.